JP4608944B2 - Film forming apparatus and film forming method - Google Patents

Description

  The present invention relates to a film forming apparatus and a film forming method, and more particularly to a film forming apparatus and a film forming method suitable for forming a carbon protective film by a CVD method (Chemical Vapor Deposition).

  Magnetic recording media such as magnetic tapes and magnetic disks are used in, for example, audio equipment, video equipment, computers, and the like, and the demand for such recording media has increased remarkably. For magnetic tape, which is one of the magnetic recording media, low cost by roll-to-roll manufacturing method (a method of forming a film while running a non-magnetic support between an unwinding roll and a winding roll) In addition, it is widely used as an image recording and data streamer because of low cost associated with mass productivity, high recording capacity, and recording retention reliability.

  Conventionally, as a magnetic recording medium, a powder magnetic material such as an oxide magnetic powder or an alloy magnetic powder is used on a nonmagnetic support, such as a vinyl chloride-vinyl acetate copolymer, a polyester resin, a urethane resin, and a polyurethane resin. A so-called coating-type magnetic recording medium prepared by applying and drying a magnetic paint dispersed in an organic binder is widely used.

  On the other hand, with increasing demand for high-density magnetic recording, metallic magnetic materials such as Co—Ni alloy, Co—Cr alloy, and Co—O are plated or vacuum thin film forming means [(vacuum evaporation method or sputtering method. , So-called metal magnetic thin film type magnetic recording medium deposited on a non-magnetic support such as polyester film, polyamide, polyimide film by so-called PVD technology (Physical Vapor Deposition) such as ion plating method] Has been proposed and attracted attention.

  As described above, the magnetic tape is mainly classified into a coating type tape in which a magnetic layer serving as a recording medium is formed by applying and drying a magnetic paint, and for example, a vapor deposition tape formed by vacuum deposition or the like.

  The latter vapor-deposited tape has excellent coercive force and squareness ratio, and the thickness of the magnetic layer can be made extremely thin, so the thickness loss during recording demagnetization and reproduction is extremely small, and the electromagnetic conversion characteristics at short wavelengths are also excellent. In addition, since there is no need to mix a binder, which is a nonmagnetic material, in the metal magnetic layer, it has a number of advantages such as an increase in the packing density of the metal magnetic material.

  In order to improve the electromagnetic conversion characteristics of this type of magnetic recording medium and obtain a larger output, when forming the metal magnetic layer of the magnetic recording medium, the metal magnetic layer is deposited obliquely, so-called Oblique vapor deposition has been proposed and put into practical use.

  By the way, in the metal magnetic thin film type magnetic recording medium, the medium tends to be smoothed in order to reduce the spacing loss for the purpose of higher density recording. However, if the surface of the magnetic layer is smooth, the substantial contact area with respect to the sliding member such as the magnetic head and the guide roller becomes large. Therefore, for example, the frictional force between the medium and the magnetic head becomes large, and the agglomeration force increases. The shearing phenomenon (so-called sticking) easily occurs, and the shearing stress generated in the medium becomes large, such as lack of running performance and durability.

  For example, an 8 mm tape inserted in an 8 mm video deck is wound around a drum through 10 or more guide pins. At that time, the tape tension and the tape traveling speed are kept constant by the pinch roller and the capstan. For example, the tension is about 20 g and the traveling speed is about 0.5 cm / s.

  In this running system, the magnetic layer of the tape is in contact with a fixed guide pin made of stainless steel. For this reason, when the friction on the tape surface increases, the tape causes stick-slip and a so-called tape squealing phenomenon occurs, which causes the playback screen to be dragged.

  In addition, the relative speed between the tape and the head is very high, and particularly in the pause state, high-speed contact is made at the same location. This causes a problem of wear of the metal magnetic layer, leading to a decrease in reproduction output. In particular, in the case of a vapor deposition tape in which a metal magnetic layer is formed by vapor deposition, this problem is further promoted because the metal magnetic layer is very thin.

  On the other hand, in a hard disk drive, CSS (contact start / stop) is a type in which the magnetic head is in contact with the magnetic disk before rotation, and when the disk starts rotating at high speed, it floats by the generated air flow. It is a device. Therefore, since the medium rubs when starting or stopping or starting, an increase in friction at that time is a big problem.

  In order to maintain the reliability at the commodity level, it is desirable that the coefficient of friction after performing the CSS operation 20,000 times is particularly 0.5 or less. In addition, since it rotates at a high speed, the occurrence of a head crash or the like due to the head and the medium is another problem.

  As described above, in a situation where sliding durability becomes severe, a technique for forming a protective film on the surface of a metal magnetic layer has been studied particularly for the purpose of improving durability.

Examples of such a protective film include a carbon film (carbon film: hereinafter the same), a quartz (SiO ₂ ) film, a zirconia (ZrO ₂ ) film, and the like.

  In particular, a diamond-like carbon (DLC: carbon mainly composed of diamond structure) film having a hardness higher than that of the carbon film is an excellent protective film, and is formed by a sputtering method, a CVD method, or the like.

  Sputtering is an ionization (plasmaization) of an inert gas such as argon gas using an electric field or a magnetic field, and the target atoms are knocked out by kinetic energy obtained by accelerating the ionized ions. . Then, the knocked-out atoms are deposited on the opposing substrate to form a target protective film.

  On the other hand, the CVD method is one of thin film formation techniques using growth in a gas phase, by decomposing a raw material gas using a chemical reaction in a high-temperature space of a gas containing a film forming substance. In this method, a film forming material is generated, and this film forming material is deposited on a substrate. A typical apparatus using the CVD method is a plasma CVD apparatus.

  And a vapor deposition tape is produced through the process of forming a metal magnetic layer, a protective film, and a lubricating layer one by one on the base material which consists of a polymer film, for example. Among them, the metal magnetic layer is deposited by vacuum evaporation, Co or Co-Ni is dissolved and evaporated by an electron beam, condensed on the base material, and further on the metal magnetic layer with a head or the like. It is necessary to form a protective film for improving durability against sliding, and a DLC (Diamond Like Carbon) protective film is formed by sputtering or plasma CVD.

  In this DLC protective film formation process, the plasma CVD method has higher film quality operability than the sputtering method, and it is easy to obtain the required film quality. Further, the film formation rate is high and the productivity is high. It is used in the process of forming a protective film during manufacture.

  In the plasma CVD method used for the manufacturing process of the vapor deposition tape, for example, a metal magnetic layer made of Co or Co-O formed on a base material is used as a cathode, and an anode is arranged at an opposing position, and a raw material is provided between these electrodes. A process gas to which a hydrocarbon gas to be gas or an argon gas for promoting decomposition is added is satisfied. In this method, a process gas is decomposed by a plasma induced by an electric field between both electrodes, and carbon having a sp2 structure represented by graphite and a sp3 structure represented by diamond is macroscopically amorphous on the cathode. It is a film-forming method to laminate in quality.

  In such a film forming method, it is necessary to improve the film quality in order to improve the film forming rate for improving productivity or to improve the durability by increasing the relative speed with the head.

  For example, in plasma CVD, increasing the plasma density by applying a magnetic field to plasma is considered to promote decomposition and recombination of process gases, and can be expected to lead to an increase in film formation rate and film quality. .

  There are many examples of applying a magnetic field to plasma in this way. For example, in order to trap electrons and increase the frequency of collision with hydrocarbon gas, physically, in a direction orthogonal to the direction of the generated electric field. It is necessary to generate magnetic field lines having a magnetic field vector component, and in particular, a cathode having a large voltage drop (strong electric field), that is, the vicinity of the metal magnetic layer on the surface of the film substrate is effective.

  In the roll-to-roll film formation method, which is a feature of the manufacturing process of the vapor-deposited tape, for example, it is necessary to cool the base material when forming the protective film on the base material made of a polymer film. The film-forming source (plasma generation region) is passed while the roll and the base film are rotated in contact with each other in synchronization. Cooling by the cooling main roll is performed by, for example, heat exchange with a refrigerant circulated and supplied from the outside of the vacuum chamber to the inside of the roll through a rotary joint or the like.

  In this case, generating magnetic lines of force in the direction perpendicular to the electric field (that is, the surface direction of the substrate) with respect to the film substrate with the metal magnetic layer (cathode) is effective in improving the film quality of the protective film to be formed. It is. As such a film forming apparatus, an apparatus in which a magnetic field generation source is installed inside a cooling roll is known (see Patent Document 1 described later).

  According to this known technique, as shown in FIG. 9, in the magnetron plasma CVD apparatus 74, the plurality of magnetic circuits 52 correspond to the size of the anode electrode (anode) 58 disposed facing the main roll 50. In this range, the main roll 50 is provided. Each magnetic circuit 52 is attached to each mounting support plate 55 so as to generate a uniform magnetic flux.

  In this way, magnetron discharge is generated in the vicinity of the surface of the traveling film base 54 by the electrons trapped by the magnetic flux generated through the non-magnetic main roll 50 from each magnetic circuit 52, and is generated on the surface of the base 54. A protective film is formed.

  In this apparatus 74, the air introduction rod 51 is connected to the inside of the main roll 50 in order to make the inside of the main roll 50 have a double wall structure and to form an atmospheric pressure region 57 that is an atmosphere separated from the plasma generation region 56. ing. A magnetic circuit 52 is fixed inside the main roll 50, and only the main roll 50 is rotated. The anode electrode 58 is disposed so as to face along a part of the surface of the main roll 50 and includes a plurality of gas introduction rods 53.

  Then, a mixed gas of the hydrocarbon gas 70 and the carrier gas 71 is introduced from the introduction rod 53 to the surface of the film base 54. Thus, the magnetron discharge is generated in the region where the high frequency discharge is sustained and the magnetic circuit 52 generates the magnetic flux outside the main roll 50 (part of the plasma generation region 56).

JP-A-11-61416 (page 3, left column, line 30 to page 4, left column, line 20, line 3)

  However, the plasma CVD apparatus 74 based on the above-mentioned Patent Document 1 needs to greatly modify an existing apparatus, and the modification becomes large and increases the cost. Moreover, in this modified structure, little consideration is given to improvements in film formation speed and film quality.

  On the other hand, it is conceivable to install the magnetic field generation source around the cathode and outside the film formation source (plasma generation region). However, when the size of the film formation source increases, the magnetic field generation source goes from the magnetic field generation source to the inside of the film formation source. Accordingly, the attenuation of the magnetic field strength increases, and the difference in magnetic field strength between the outside and inside of the film forming source increases. As a result, there is a problem that a region where the magnetic field effectively acts is limited to a part of the film forming source, and a film thickness distribution (in-plane variation in film thickness) occurs due to the magnetic field strength distribution.

  The present invention has been made in view of the above-described conventional situation, and an object of the present invention is to form a film forming apparatus and a film forming method capable of arranging a magnetic field generation source relatively easily and particularly improving film quality. Is to provide.

  That is, the present invention uses a cathode on the side of an object to be deposited, and decomposes the source gas under the action of plasma generated by an electric field generated between the cathode and the anode facing the cathode. In a film forming apparatus configured to form a film on a film formation target, a magnetic field generation source is disposed on the opposite side of the anode from the cathode, and the magnetic field generation source causes a surface of the film formation target to be formed on the anode. Further, the present invention relates to a film forming apparatus characterized in that a magnetic field acts in a direction crossing the direction of the electric field.

  The present invention also provides a cathode on the side of an object to be deposited, and decomposes the source gas under the action of plasma generated by an electric field generated between the cathode and the anode facing the cathode. In a film forming method for forming a film on a film forming body, a magnetic field generation source is disposed on the opposite side of the anode from the cathode, and the direction of the electric field is set on the surface of the film formation body by the magnetic field generation source. The present invention relates to a film forming method characterized by applying a magnetic field in a crossing direction.

  According to the present invention, since the magnetic field generation source is disposed on the opposite side of the anode with respect to the anode, the magnetic field generation source is disposed relatively easily compared to the case of being disposed inside the cathode. A film forming apparatus can be easily configured.

  Since the magnetic field generation source is configured so that a magnetic field acts on the surface of the deposition target body in a direction (particularly, a direction orthogonal to the direction of the electric field), the source gas is decomposed and recombined. In particular, it is possible to improve the film quality of the formed film and to apply a sufficiently strong magnetic field over a wide range.

  In the present invention, in order to reliably obtain the effects of the present invention, film formation is performed by a chemical vapor deposition method involving decomposition of the source gas in a reduced-pressure atmosphere under generation of plasma, and in the plasma generation region. In the vicinity, the magnetic field generation source such as a permanent magnet or an electromagnet is disposed on the back side of the anode where the plasma is not in direct contact, and in the direction perpendicular to the direction of the electric field in the vicinity of the surface of the film formation target. It is desirable that the magnetic field acts to have a vector component.

  In this case, electrical interference between the anode to which a high voltage is applied and the magnetic field generation source and the ground is prevented, and the plasma generation region is limited between the anode and the cathode to efficiently generate plasma. In order to generate, the magnetic field generating source is electrically connected to the anode and is at the same potential, and is disposed in the container through an electrically insulating structure and ground potential of the vacuum chamber outside the container. It is desirable that both parts are electrically insulated.

  In this case, the space between the cathode and the anode in the inner space of the container is a plasma generation space, the magnetic field generation source side is a source gas introduction space, and the source gas introduced space is introduced from the source gas introduction space. It is desirable that the source gas be guided to the plasma generation space through the gas passage part of the anode.

  Here, in order to simultaneously maintain the gas pressure uniformity in the plasma generation space while securing the space of the magnetic field generation source, the yoke portion of the magnetic field generation source provided with the source gas passage portion is It is desirable that the magnetic flux density is difficult to saturate and has a sufficient gas permeable sectional shape.

  In this case, it is desirable that both the anode and the magnetic field generation source are made of a gas permeable porous structure in order to facilitate introduction of gas from the source gas introduction space into the plasma generation space.

  Further, it is preferable that the film formation target is a nonmagnetic support with a metal magnetic layer for a magnetic recording medium, and a protective film made of amorphous carbon is formed on the metal magnetic layer. This protective film is desirably formed by decomposition of a hydrocarbon-based gas.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  With reference to FIG. 1, the configuration of a plasma CVD apparatus 24A (film forming apparatus) according to the present embodiment will be described. The apparatus 24A forms a carbon film (particularly a DLC film) as a surface protective film on the magnetic layer while unwinding the film base 4 for a magnetic recording medium having a magnetic layer as a cathode made of a metal magnetic thin film. This is a roll-to-roll system.

  In this plasma CVD apparatus 24A, the film base 4 with a magnetic layer for a magnetic recording medium is transferred from the unwinding roll 2 to the guide rollers 3a, 3b, 3c constituting the roll running system 12, and the reaction tube 9 (container). Are sequentially conveyed in the order of the cooling main roll 5, the guide rollers 3d, 3e, 3f, and the take-up roll 1 that are disposed opposite to each other. The film base 4 is transported while being supported by this transport system, and the metal magnetic layer of the film base functions as a cathode. However, for the sake of simplicity, the film substrate is illustrated as the cathode 4.

  Inside the reaction tube 9, an anode 8 composed of a mesh part 8 a having sufficient gas permeability is incorporated facing the roll 5, and this anode 8 is about +500 to 2000 V by a DC (direct current) power source 10. A voltage is applied. Further, a raw material gas (for example, ethylene gas or propylene gas) 20 containing hydrocarbon as a main component is mixed with a carrier gas 21 and introduced into the reaction tube 9 from the reaction tube back surface portion 19 through the valve 15a.

  Opposite to the reaction tube 9, a cylindrical rotatable main roll 5 is installed with a minute gap 7 (for example, about 1 mm). The inside of the vacuum chamber 6 of the device 24A is maintained in a reduced pressure atmosphere of, for example, 0.5 Pa or less by the vacuum pump 16 through the valve 15b.

  In addition, a hydrocarbon-based gas (raw material such as ethylene gas) 20 introduced from the gas introduction unit 18 is decomposed by plasma induced by a DC electric field generated in the plasma generation region 36 in the reaction tube 9. Then, a carbon film (DLC film) serving as a protective film is deposited on the metal magnetic layer of the film base 4 that is sequentially conveyed by the main roll 5.

  For example, the film base 4 has a thickness of about 10 μm and is made of a polymer material such as PET (polyethylene terephthalate) or aramid. In the vacuum deposition in the previous step, a metal magnetic layer made of, for example, CoO is formed to a thickness of 200 nm. (Surface resistance is 150Ω / sq) is formed on the surface.

  Further, in order to suppress thermal deformation of the film base 4 due to plasma radiant heat during the formation of the protective film, a cooling main roll 5 whose temperature is controlled in the roll travel system 12 is provided and brought into contact with the film base 4. Heat removal is performed by synchronous rotation.

  A process gas composed of a mixed gas of a hydrocarbon gas such as ethylene, propylene, acetylene, and toluene, which is a raw material for DLC (diamond-like carbon), and, for example, argon gas, which is a carrier gas 21, is supplied at a predetermined flow rate from the gas introduction unit 18. Controlled and introduced into the gas introduction region 35 from the reaction tube rear surface portion 19, passes through the gas-permeable porous portion 14 of the magnetic field generation portion 17, and further passes through the mesh portion 8 a of the anode 8, and flows to the cathode 4 side. It is diffused into the vacuum chamber 6 through the gap 7 between the cooling main roll 5 and the reaction tube 9 and exhausted.

  Here, the pressure difference between the inside of the vacuum chamber 6 and the inside of the reaction tube 9 is changed by changing the width of the gap 7 between the cooling main roll 5 and the reaction tube 9 from the outside of the vacuum chamber 6. The gas to be introduced can be controlled to a predetermined process gas pressure.

  The anode 8 has a metal mesh portion 8a (gas passage portion) for allowing the process gas introduced from the back surface to pass therethrough and for making the applied voltage uniform within the electrode surface. The constituent material of the metal mesh portion 8a is, for example, an inexpensive copper or austenitic stainless material that is a good electrical conductor and a non-magnetic material in order to suppress the magnetic influence of the magnetic field generating portion 17 installed on the back side thereof. Etc.

  The anode 8 and the magnetic field generator 17 are electrically connected to each other and have the same potential, and the reaction tube 9 and the vacuum chamber 6 are partially insulated through an insulating layer 25 (insulating structure) shown in the drawing. In the reaction tube 9, an electric field 22 indicated by a straight arrow is generated between the anode 8 and the cathode 4, and a magnetic field 23 indicated by a dashed curved arrow is generated by the permanent magnet 11 of the magnetic field generation source. The situation that has occurred is illustrated.

  Actually, the entire inner surface of the reaction tube 9 is covered with the insulating layer 25 in order to effectively generate plasma in the plasma generation region 36 inside the reaction tube 9, and the reaction tube 9 has a thermal strength so as to have thermal strength. It is preferable to use a material such as ceramic or quartz.

  The generation situation of the magnetic field 23 will be described in detail with reference to FIG. 2. A DC electric field 22 is generated by the power source 10 in the plasma generation region 36 between the cathode 4 and the anode 8 made of a metal magnetic layer on the film substrate 4. In this state, the magnetic field generator 17 (magnetic circuit: magnetic field generation source) composed of the permanent magnet 11 and the yoke 13 leaks from the north pole of the central permanent magnet 11 toward the south pole of the adjacent permanent magnet 11, for example. A magnetic field 23 is generated. As a result, a vector component of the magnetic field 23 is generated on the surface of the metal magnetic layer of the film substrate along the direction crossing the direction of the electric field 22, particularly in the direction 23 a orthogonal thereto.

  Here, for example, when the distance between the cathode 4 and the anode 8 is set to 60 mm, the strength of the magnetic field (magnetic flux density) is about 70 mT near the surface of the anode 8, and the surface of the cathode of the film base 4 In the above, a magnetic field of about 3.3 mT (intensity of a component orthogonal to the electric field: about 2.6 mT) is generated. For example, when the distance between the cathode 4 and the anode 8 is set to 180 mm, the intensity of the magnetic field on the surface of the cathode 4 is about 0 mT.

  The strength of the magnetic field is weak on the surface of the cathode of the film substrate 4, but a part of the magnetic field lines in the vicinity pass through a part of the cathode of the film substrate 4, thereby Then, the magnetic field 23a is easily generated in a direction orthogonal to the direction of the electric field 22.

  In order for the process gas introduced from the back side of the anode 8 to be uniformly dispersed in the plasma generation region 36 in the reaction tube 9 through the porous portion 14, the gas introduction region 35, and the mesh portion 8 a of the yoke 13 in order, It may be possible to achieve uniform dispersion of the process gas by providing a porous dispersion plate in the process gas introduction hole. However, since there is a space limitation between the dispersion plate and the magnetic field generation source, the yoke 13 that holds the permanent magnet 11 with a cross-sectional area that is equal to or less than the saturation magnetic flux density is similar to the above gas dispersion plate. By providing the porous portion 14 having the above structure, the yoke 13 has a function having both the performance as a yoke and the gas dispersion performance.

  In addition, since the magnetic flux density is easily saturated when the sectional area of the permanent magnet 11 decreases, it is desirable that the sectional area is as large as possible.

  FIG. 3 shows an exploded view of a magnetic circuit composed of a permanent magnet (magnet) 11 and a yoke 13 constituting the magnetic field generator 17 and the anode 8. A cross section taken along the line II-II 'in this figure corresponds to FIG.

  The anode 8 provided between the plasma generation region 36 and the magnetic field generation unit 17 includes a mesh portion 8a and a support frame portion 26 that supports the mesh portion. The permanent magnet 11 forming the gas introduction region 35 includes a frame portion 27 and an H-shaped portion 28 disposed in the frame portion 27. Moreover, the yoke 13 has a porous portion 14 as a plurality of holes for allowing gas to pass through, for example, a plate-shaped iron plate. The iron yoke 13 prevents a leakage magnetic field from being generated at the back of the magnetic field generator 17.

  Here, since the material of the permanent magnet (magnet) 11 needs to have thermal stability against radiant heat from plasma, it is preferable to use ferrite or samarium cobalt. In this embodiment, for example, a permanent magnet 11 made of an anisotropic ferrite material (surface magnetic flux density 170 mT) and an iron yoke 13 constitute a magnetic circuit.

  The magnetic field generator 17 constituting such a magnetic circuit is installed on the back side of the anode 8 to which a high voltage is applied. However, by making electrical contact with the anode 8, there is no need to perform insulation treatment between the two. Yes.

  In FIG. 4, the surface protective film 31 was formed on the film base material 4 in which the metal magnetic layer 30 was formed on the base material 29 (nonmagnetic support) by the plasma CVD apparatus 24A, and this was wound up. A magnetic recording medium 32 such as a magnetic tape that is later unwound and spliced to a desired width is shown.

  FIG. 5 is the same as the above-described embodiment except that instead of the permanent magnet 11 described above, a plasma CVD apparatus 24B using an electromagnet formed by winding a coil 33 around a core 34 as the magnetic field generator 17 is used. It is.

  For the magnetic field generation source 17 installed on the back side of the anode 8, a magnetic circuit using a permanent magnet 11 that is inexpensive and can increase the magnetic field strength generated in a limited space is suitable. As described above, a magnetic circuit can also be configured by an electromagnet using the coil 33.

  When a magnetic field is generated by such an electromagnet, the magnetic field strength generated by the current flowing through the coil 33 can be freely changed, and the magnetic field strength in the vicinity of the surface of the film substrate (cathode) 4 can be changed according to conditions such as the distance between electrodes. The magnetic field strength can be controlled by changing according to.

  In addition, in the present embodiment, the same operations and effects as described above can be obtained.

  As described above, according to the present embodiment, on the opposite side of the anode 8 from the cathode 4 made of the metal magnetic layer, the magnetic circuit portion made of the permanent magnet 11 and the yoke 13 or the magnetic circuit made of an electromagnet, That is, since the magnetic field generation unit 17 is arranged, the magnetic field generation unit 17 is arranged relatively easily, and the plasma CVD apparatuses 24A and 24B that can perform plasma CVD efficiently under the action of both the magnetic field and the electric field are configured. be able to. In particular, since the magnetic field generation unit 17 is installed on the back side of the anode 8, the modification of the plasma CVD apparatus for obtaining the effect of the magnetic field can be minimized.

  In this case, since the magnetic field generating unit 17 generates the magnetic field vector 23a on the surface of the film substrate (cathode) 4 in a direction crossing the direction of the electric field 22, the reaction gas is generated when the plasma is generated by the electric field. By the trap of the decomposition product, the quality of the protective film formed on the cathode surface where a voltage drop is likely to occur can be improved.

  In addition, the anode 8 and the magnetic field generator 17 are electrically connected to have the same potential and insulated from the reaction tube 9 and the vacuum chamber 6, so that the anode 8 to which a high voltage is applied and the magnetic field generation adjacent to the anode 8 are generated. Electrical interference between the unit 17 and the ground source can be easily eliminated.

  Furthermore, by making the magnetic field generation unit 17 the above-described porous structure, both the space for the magnetic field generation unit 17 is ensured and the gas pressure in the reaction tube 9 is prevented from becoming uneven. Is possible.

  Next, the result of detailed evaluation of the DLC film 31 that is the surface protective film formed in the present embodiment will be described.

FIG. 6 shows the carbon composition of the DLC film measured by general Raman spectroscopy. Incident light used here was an argon gas excitation laser wavelength 514.5 nm, were analyzed intensity spectrum measurement wavenumber of reflected scattered light as 1800 cm ^-1 from 1000 cm ^-1.

The intensity spectrum of a typical DLC has a curved shape with wavenumbers having peaks at around 1350 cm ⁻¹ (D-band) and around 1525 cm ⁻¹ (G-band). The former is a disordered area as a carbon bond structure. (Ad) is attributed to the sp3 structure, and the latter is attributed to the sp2 structure in the graphite area (Ag). Furthermore, the baseline of the background area (B) and the area sum of the disorder area (Ad) and the graphite area (Ag) represented by Ad + Ag are shown (see Japanese Patent Laid-Open No. 2000-207736).

  Here, the principle of the measurement method by Raman spectroscopy will be briefly explained. In general, the Raman scattering measurement apparatus mainly comprises four parts, ie, an excitation light source, a sample part, a dispersion system, and a detector. The excitation light is an ion gas laser. The sample part is composed of an optical system for sample irradiation and collection of scattered light.

  The Raman scattered light is collected on the spectrometer slit by a condenser lens or a condenser mirror. This scattered light is dispersed by a double monochromator in which a single spectroscope is connected in series and detected by a detector. Although a photomultiplier is used as a detector, an optical multi-channel detector has been used in recent years. Since the optical multichannel detector can simultaneously measure the spectrum, it has an advantage that the measurement time is only a few seconds.

  Since the Raman spectrum obtained in this way is unique to the substance, this allows the substance to be fixed. Further, it is proportional to the Raman scattering intensity and the substance amount at a specific wavelength.

  When structurally classifying the carbon material, it can be divided into diamond, graphite, and amorphous carbon considered to be in an intermediate state. Raman spectroscopy is specifically sensitive to these carbons and is sensitive to changes in abundance.

Here, as an evaluation method using the Raman spectroscopy, the superposition of the resultant intensity spectrum at between wave number of from 1000 cm ^-1 1800 cm ^-1, and two Gaussian functions (Ad and Ag) and the straight line (B) The ratio Ad / Ag, the ratio (Ad + Ag) / B, and the area sum (Ad + Ag) were obtained from the area value Ad, area value Ag, and area B of the three regions shown in FIG.

  In general, Ad / Ag corresponds to the hardness of DLC, and (Ad + Ag) / B is said to have a correlation with the wear resistance of DLC (see JP-A-2001-423529).

  The area sum (Ad + Ag) is said to have a correlation with the film thickness of DLC (see JP 2000-207736). In the results, the conversion value calculated from this correlation function is expressed as the film thickness. Yes.

  Next, a specific example will be described in which a DLC film is formed on a film substrate 4 in which a metal magnetic thin film is provided on a nonmagnetic support using, for example, the plasma CVD apparatus shown in FIGS. .

The film forming conditions were as follows.
Source gas: C ₂ H ₄ / Ar = 110 sccm / 28 sccm
Reaction pressure (in reaction tube): 30 Pa
Introduced power (discharge voltage): DC1.2kV
Magnetic field generation source: Anisotropic ferrite permanent magnet (surface magnetic flux density 170 mT), iron yoke

  The film quality and deposition rate of the DCL film when the distance between the electrodes 4-8 was changed were compared between the case where the magnetic field generated by the magnetic field generation source was present and the case where the magnetic field was not present.

  FIG. 7 shows the correlation between Ad / Ag (corresponding to the hardness of DLC) and the distance between electrodes (A), and the correlation between (Ad + Ag) / B (corresponding to the wear resistance of DLC) and the distance between electrodes (B ) And the correlation (C) between the deposition rate and the distance between the electrodes.

  First, as shown in FIG. 7A, when a magnetic field is present, Ad / Ag is about 0.53 when the distance between the electrodes is 60 mm, and Ad / Ag is about 0.1 when the distance between the electrodes is 180 mm. Therefore, when the distance between the electrodes is increased, Ad / Ag corresponding to the hardness of DLC slightly increases.

  On the other hand, when there is no magnetic field, Ad / Ag is about 0.56 when the distance between the electrodes is 60 mm, and Ad / Ag is about 0.56 when the distance between the electrodes is 180 mm. Even if the distance is increased, it can be said that there is no change in Ad / Ag corresponding to the hardness of DLC.

  Therefore, it can be seen from this result that when the distance between the electrodes is increased in the presence of a magnetic field, the hardness of DLC slightly increases as compared to the case without a magnetic field.

  Next, as shown in FIG. 7B, in the presence of a magnetic field, when the interelectrode distance is 60 mm, (Ad + Ag) / B is about 0.83, and when the interelectrode distance is 180 mm, (Ad + Ag) / Since B is about 0.5, (Ad + Ag) / B corresponding to the wear resistance of DLC increases remarkably when the distance between the electrodes is decreased.

  In contrast, in the absence of a magnetic field, (Ad + Ag) / B is about 0.48 when the distance between the electrodes is 60 mm, and (Ad + Ag) / B is about 0.48 when the distance between the electrodes is 180 mm. Therefore, even if the distance between the electrodes is increased, no change is observed in (Ad + Ag) / B corresponding to the wear resistance of DLC.

  According to this result, there is almost no difference between the case where the magnetic field is present and the case where the magnetic field is not present when the distance between the electrodes is 180 mm. However, as the distance between the electrodes becomes smaller, the magnetic field is present as (Ad + Ag) / When B increases, the wear resistance of DLC is greatly improved. In particular, when the distance between the electrodes is 60 mm, it is about 1.7 times or more that without a magnetic field. Therefore, when a magnetic field is present, the wear resistance of the DLC can be remarkably improved by reducing the distance between the electrodes to 180 mm or less.

  Next, as shown in FIG. 7C, in the relationship between the deposition rate and the interelectrode distance, when a magnetic field is present, the deposition rate is about 780 nm / min when the interelectrode distance is 60 mm. When the distance between the electrodes is 180 mm, the film formation speed is about 710 nm / min. Therefore, when the distance between the electrodes is increased, the film formation speed slightly decreases.

  On the other hand, in the absence of a magnetic field, the deposition rate is about 670 nm / min when the interelectrode distance is 60 mm, and the deposition rate is about 680 nm / min when the interelectrode distance is 180 mm. Even when the distance is increased, the film formation rate hardly changes.

  According to this result, there is almost no difference between the case where the magnetic field is present and the case where the magnetic field is not present when the distance between the electrodes is 180 mm, but the case where the magnetic field is present when the distance between the electrodes is 60 mm as compared with the case without the magnetic field. Therefore, when the magnetic field is present, the deposition rate can be improved by reducing the distance between the electrodes.

  From the results shown in FIG. 7, it is possible to improve the film quality of DLC by the synergistic effect of the magnetic field and the plasma, and as a characteristic of DLC obtained by Raman spectroscopic evaluation, the ratio of Ad / Ag corresponding to hardness is almost Without changing, each value of (Ad + Ag) and (Ad + Ag) / B can be increased to improve wear resistance. From the film thickness converted from (Ad + Ag), it can be seen that the film formation rate can be increased by about 1.2 times.

  Next, in the above, it was examined whether or not the quality of the DLC film and the film formation rate change depending on the type of source gas.

The film forming conditions were as follows.
Source gas: C ₂ H ₄ / Ar = 110 sccm / 28 sccm
: C ₃ H ₆ / Ar = 110 sccm / 28 sccm
Reaction pressure (in reaction tube): 30 Pa
Introduced power (discharge voltage): DC1.2kV
Magnetic field source: Same as above

FIG. 8 shows the correlation (A) between Ad / Ag and the distance between electrodes for a DLC film formed using C ₂ H ₄ or C ₃ H ₆ when a magnetic field is present under these conditions. , (Ad + Ag) / B and the interelectrode distance (B), and the correlation between the deposition rate and the interelectrode distance (C) are shown.

First, as shown in FIG. 8A, when C ₂ H ₄ is used, Ad / Ag is about 0.53 when the distance between the electrodes is 60 mm, and Ad / Ag when the distance between the electrodes is 180 mm. Since it is about 0.58, when the distance between electrodes is increased, Ad / Ag corresponding to the hardness of DLC slightly increases.

When C ₃ H ₆ is used, Ad / Ag is about 0.6 when the distance between the electrodes is 60 mm, and Ad / Ag is about 0.57 when the distance between the electrodes is 180 mm. When the distance is increased, Ad / Ag corresponding to the hardness of DLC decreases.

According to this result, there is almost no difference between the case where C ₂ H ₄ is used and the case where C ₃ H ₆ is used when the distance between the electrodes is 180 mm. However, when the distance between the electrodes is 60 mm, C ₂ H ₄ Ad / Ag in the case of using C ₃ H ₆ is larger than Ad / Ag in the case of using C, which is about 1.1 times. When C ₃ H ₆ is used, the distance between the electrodes is reduced. As a result, the hardness of DLC can be improved.

Next, as shown in FIG. 8B, when C ₂ H ₄ is used, when the distance between the electrodes is 60 mm, (Ad + Ag) / B is about 0.83, and when the distance between the electrodes is 180 mm ( Since (Ad + Ag) / B is about 0.5, (Ad + Ag) / B corresponding to the wear resistance of DLC is remarkably improved when the distance between the electrodes is decreased.

When C ₃ H ₆ is used, (Ad + Ag) / B is about 0.78 when the distance between the electrodes is 60 mm, and (Ad + Ag) / B is about 0.35 when the distance between the electrodes is 180 mm. Therefore, when the distance between the electrodes is reduced, the value is lower than that of C ₂ H ₄ , but (Ad + Ag) / B corresponding to the wear resistance of DLC is remarkably improved.

As a result, in both cases of using C ₂ H ₄ and using C ₃ H ₆ , the wear resistance of DLC is reduced when the distance between the electrodes is 180 mm to the distance between the electrodes is 60 mm. As the distance is reduced, the wear resistance of the DLC can be remarkably improved. In particular, when C ₂ H ₄ is used, it can be further improved.

Next, as shown in FIG. 8C, when C ₂ H ₄ is used, the deposition rate is about 780 nm / min when the distance between the electrodes is 60 mm, and the deposition rate when the distance between the electrodes is 180 mm. Is about 720 nm / min. Therefore, when the distance between the electrodes is increased, the deposition rate is decreased.

When C ₃ H ₆ is used, the deposition rate is about 1100 nm / min when the interelectrode distance is 60 mm, and the deposition rate is about 1040 nm / min when the interelectrode distance is 180 mm. As the distance is increased, the deposition rate decreases.

As a result, when C ₂ H ₄ is used and when C ₃ H ₆ is used, Ad / Ag and film formation rate are larger when C ₃ H ₆ is used, and C ₂ H ₄ is reduced. In the case of use, (Ad + Ag) / B becomes larger.

  As mentioned above, although embodiment and the specific example were described for this invention, this invention is not limited to these examples at all, and can be suitably changed in the range which does not deviate from the meaning of invention.

  For example, the size, shape, arrangement, material, magnetic field strength, etc., of the permanent magnet 11 and the iron yoke can be changed according to conditions such as the distance between the anode 8 and the film substrate (cathode) 4. .

  Further, the gas introduction part 18 of the reaction tube 9 may be provided so as to be introduced from the side surface of the reaction tube 9.

  Moreover, when forming DLC with respect to the base material which does not have metal layers, such as an insulating film, the metal main rolls 5 for cooling can be used as a cathode.

  In addition, the film formation target on which the protective film is formed may be not only a film shape but also a plate shape, or a fixed type.

  Further, as the structure of the magnetic field generation unit 17, the permanent magnet 11 and an electromagnet including the coil 33 and the core 34 can be combined.

  As the plasma CVD apparatus, a known plasma generation method can be applied. For example, the electrons emitted from the hot cathode collide with gas molecules before flowing into the anode and ionize or excite them to create plasma, the electrons extracted when ions flow into the cold cathode Plasma is generated by high-frequency electromagnetic induction by providing a bipolar discharge type that creates a plasma by colliding with gas molecules before going straight toward the anode and flowing in, a magnetic field converging type typified by a magnetron discharge type, and a high-frequency coil. There are electrodeless type that produces the ECR, and ECR type (Electron Cyclotron Resonance) that uses microwaves.

  In addition to the above, methane, ethane, ethylene, acetylene, toluene and the like can be used for the hydrocarbon gas 20. Even if these raw materials are used, a carbon film (mainly amorphous structure) can be used. Carbon films), DLC films (carbon films mainly having a diamond structure), diamond films, and the like can be sufficiently obtained.

  In particular, this protective film is preferably a DLC film, and after forming the carbon film by a CVD method or the like, irradiating the carbon film with high-energy ions (for example, nitrogen ions) to promote DLC formation. Is possible.

In addition to the carbon film, the protective film can be sufficiently formed using other commonly used raw materials. Examples include CrO ₂ , Al ₂ O ₃ , BN, Co oxide, MgO, SiO ₂ , Si ₃ O ₄ , SiN _x , SiC, SiN _x —SiO ₂ , ZrO ₂ , TiO ₂ , and TiC. . These may be a single layer film, a multilayer film or a composite film.

  In addition, a metallic magnetic thin film is formed as a magnetic layer by depositing a ferromagnetic metal material on a non-magnetic support, and this metal magnetic material is used for ordinary vapor deposition tapes and the like. Any material can be used.

  For example, ferromagnetic metals such as Fe, Co, Ni, Fe—Co, Co—Ni, Fe—Co—Ni, Fe—Cu, Co—Cu, Co—Au, Co—Pt, Mn—Bi, Mn Examples include ferromagnetic alloys such as -Al, Fe-Cr, Co-Cr, Ni-Cr, Fe-Co-Cr, Co-Ni-Cr, and Fe-Co-Ni-Cr. These may be a single layer film or a multilayer film.

  Furthermore, in the case of a non-magnetic support and a metal magnetic thin film, or in the case of a multilayer film, an underlayer or an intermediate layer may be provided in order to improve the adhesion between each layer and control the coercive force.

  In addition, as a means for forming a metal magnetic thin film, a vacuum evaporation method in which a ferromagnetic material is heated and evaporated under vacuum and deposited on a nonmagnetic support, an ion plating method in which the ferromagnetic material is evaporated in a discharge, A so-called PVD (Physical Vapor Deposition) technique such as a sputtering method in which glow discharge is generated in an atmosphere containing argon as a main component and atoms on the target surface are knocked out by the generated argon ions may be used.

  Moreover, a well-known material can be used also as a nonmagnetic support body. For example, in addition to polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, polyolefin resins, cellulose derivatives, vinyl resins such as polyvinyl chloride, and the like can be given. The form is not limited at all, and any form such as a tape, a sheet, and a drum may be used.

  Further, in the metal magnetic thin film type magnetic recording medium described above, a backcoat layer or the like may be formed as necessary. That is, in the same manner as in the known method, a non-magnetic pigment such as carbon is kneaded with a binder such as vinyl chloride-vinyl acetate copolymer and an organic solvent to prepare a coating material for a back coat layer, which is supported by a non-magnetic support. It is formed by applying to the surface opposite to the magnetic layer of the body, but any conventionally known binder or organic solvent can be used at this time, and it is not limited at all. Absent.

  In addition to the above-described metal thin film type magnetic recording medium, a so-called coating type magnetic material in which a magnetic coating containing fine magnetic particles and a resin binder is applied on a nonmagnetic support and used as a magnetic layer. You may apply to a recording medium.

  In addition to the magnetic recording medium, the present invention can also be applied to a case where a thin film such as a surface protective film is formed on an optical device, an element, a semiconductor device, or the like.

1 is a schematic cross-sectional view of a plasma CVD apparatus according to a first embodiment of the present invention. It is an expanded sectional view of a magnetic field generation part. FIG. 3 is an exploded perspective view of the magnetic field generation unit. 2 is a cross-sectional view of the magnetic recording medium. It is a schematic sectional drawing of the plasma CVD apparatus by the 2nd Embodiment of this invention. It is a graph showing the intensity spectrum of DLC. Graphs (A) and (Ad + Ag) representing the correlation between Ad / Ag (corresponding to the hardness of DLC) and the distance between the electrodes when the film is formed according to the present invention, with and without a magnetic field. FIG. 5 is a graph (B) representing the correlation between / B (corresponding to the wear resistance of DLC) and the interelectrode distance, and a graph (C) representing the correlation between the film formation rate and the interelectrode distance. Similarly, graphs (A) and (Ad + Ag) / B (corresponding to the wear resistance of DLC) showing the correlation between Ad / Ag (corresponding to the hardness of DLC) and the distance between the electrodes when the source gas type is changed ) And the distance between the electrodes (B), and the graph (C) showing the correlation between the deposition rate and the distance between the electrodes. It is a schematic sectional drawing of the plasma CVD apparatus by a prior art example.

Explanation of symbols

1 ... take-up roll, 2 ... unwind roll,
3a, 3b, 3c, 3d, 3e, 3f ... guide rollers,
4 ... Film substrate (cathode), 5 ... Main roll for cooling, 6 ... Vacuum chamber,
7 ... Gap part, 8 ... Anode, 8a ... Mesh part, 9 ... Reaction tube, 10 ... DC power source,
11 ... Permanent magnet (magnet), 13 ... Yoke, 14 ... Porous part,
16 ... Vacuum pump, 17 ... Magnetic field generation unit, 18 ... Gas introduction unit, 19 ... Rear side of reaction tube,
20 ... hydrocarbon gas, 21 ... carrier gas, 22 ... electric field, 23 ... magnetic field,
24A, 24B ... Plasma CVD apparatus, 25 ... Insulating layer, 26 ... Support frame,
27 ... Frame part, 28 ... H-shaped part, 29 ... Base material, 30 ... Metal magnetic layer,
31 ... Surface protective film, 32 ... Magnetic recording medium, 33 ... Coil, 34 ... Core,
35 ... Gas introduction region, 36 ... Plasma generation region

Claims (13)

The side of the deposition target to be deposited is used as a cathode, and the source gas is decomposed under the action of an electric field generated between the cathode and the anode facing the cathode to form a film on the deposition target. A magnetic field generation source is disposed on the opposite side of the anode from the cathode, and the magnetic field acts on the surface of the film formation body in a direction crossing the direction of the electric field by the magnetic field generation source. The film is formed by chemical vapor deposition with decomposition of the source gas under generation of plasma in a reduced-pressure atmosphere, and the plasma is not in direct contact in the vicinity of the plasma generation region. wherein is the arrangement the magnetic field generating source on the back side of the anode, the vicinity of the surface of the deposition target object, the magnetic field acts in a direction perpendicular to the direction of the electric field, a film forming apparatus,
Wherein the magnetic field generating source, wherein the anode and are electrically connected while being at the same potential are disposed in the container via an electrical insulation structure and is electrically insulated with the vacuum chamber outside the container Yes ,
Deposition device . Of the internal space of the container, the space between the cathode and the anode is a plasma generation space, the magnetic field generation source side is a source gas introduction space, and the source gas introduced from the source gas introduction space is The film forming apparatus according to claim 1 , wherein the film forming apparatus is guided to the plasma generation space through a gas passage portion of an anode. 3. The film forming apparatus according to claim 2 , wherein a yoke part of the magnetic field generation source provided with the source gas passage part has a sufficient cross-sectional shape in which a magnetic flux density hardly saturates and gas permeability is sufficient. The film forming apparatus according to claim 3 , wherein both the anode and the magnetic field generation source are made of a gas permeable porous structure.   The film forming apparatus according to claim 1, wherein the magnetic field generation source includes a permanent magnet or an electromagnet.   2. The composition according to claim 1, wherein the film formation target is a nonmagnetic support with a metal magnetic layer for a magnetic recording medium, and a protective film made of amorphous carbon is formed on the metal magnetic layer. Membrane device. The film forming apparatus according to claim 6 , wherein the protective film is formed by decomposition of a hydrocarbon-based gas. The side of the deposition target to be deposited is used as a cathode, and the source gas is decomposed under the action of an electric field generated between the cathode and the anode facing the cathode to form a film on the deposition target. A magnetic field generation source is disposed on the opposite side of the anode from the cathode, and a magnetic field is applied to the surface of the film-forming body by the magnetic field generation source in a direction crossing the direction of the electric field, thereby reducing the reduced pressure atmosphere. The film is formed by chemical vapor deposition with decomposition of the source gas under plasma generation, and the magnetic field is generated on the back side of the anode where the plasma does not directly contact in the vicinity of the plasma generation region. source disposed, the vicinity of the surface of the deposition material, Ru allowed to act the magnetic field in a direction perpendicular to the direction of the electric field, a film forming method,
Wherein the magnetic source, while said anode and electrically connected to the same potential, placed in an electrically insulating structure through the vessel and electrically insulated with the vacuum chamber outside the container,
Film forming method . Plasma is generated between the cathode and the anode in the inner space of the container, a source gas is introduced to the magnetic field generation source side, and the introduced source gas is introduced from the gas passage portion of the anode. The film forming method according to claim 8 , wherein the film forming method is led between a cathode and the anode. The film forming method according to claim 9 , wherein both the anode and the magnetic field generation source are formed of a gas permeable porous structure. The film forming method according to claim 8 , wherein a permanent magnet or an electromagnet is used as the magnetic field generation source. The film formation according to claim 8 , wherein the film formation target is a nonmagnetic support with a metal magnetic layer for a magnetic recording medium, and a protective film made of amorphous carbon is formed on the metal magnetic layer. Way . The film forming method according to claim 12 , wherein the protective film is formed by decomposition of a hydrocarbon-based gas.

Images